This invention relates to an aqueous based coating composition and in particular to an aqueous thermosetting acrylic enamel that provides a high quality finish for the exterior of automobile and truck bodies.
Thermosetting acrylic enamels are well known in the art as shown by Frazier et al. U.S. Pat. No. 2,681,897, issued June 22, 1954; Vasta U.S. Pat. No. 3,338,860, issued Aug. 29, 1967; Fisk et al. U.S. Pat. No. 3,365,414, issued Jan. 23, 1968; Vasta U.S. Pat. No. 3,622,651, issued Nov. 23, 1971; and Parker U.S. Pat. No. 3,637,546, issued Jan. 25, 1972. These acrylic enamels are all solvent based systems and do not provide a non-air-polluting finish. Taft U.S. Pat. No. 3,661,827, issued May 9, 1972 is directed to a process for preparing a water dispersible acrylic enamel composition but this product does not meet the needs of the automobile and truck manufacturing industry for a high quality water based finish.
The novel aqueous thermosetting acrylic enamel coating composition of this invention utilizes a particular acrylic polymer having a uniform composition and having a balance or hydroxyl and carboxyl groups in combination with a water dispersible or water soluble cross-linking agent such as an alkylated melamine formaldehyde resin to form a high quality finish useful for the exterior of automobile and truck bodies.